Add widget utility class. Add static method to determine if user can modify widgets in the specified room.

src/WidgetUtils.js

@@ -0,0 +1,53 @@
+/*
+Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2017 Vector Creations Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import MatrixClientPeg from './MatrixClientPeg';
+
+export default class WidgetUtils {
+
+    /* Returns true if user is able to send state events to modify widgets in this room
+     * @param roomId -- The ID of the room to check
+     * @return Boolean -- true if the user can modify widgets in this room
+     */
+    static canUserModifyWidgets(roomId) {
+        if (!roomId) {
+            throw new Error('No room ID specified');
+        }
+
+        const client = MatrixClientPeg.get();
+        if (!client) {
+            throw new Error('User must be be logged in');
+        }
+
+        const room = client.getRoom(roomId);
+        if (!room) {
+            throw new Error(`Room ID ${roomId} is not recognised`);
+        }
+
+        const me = client.credentials.userId;
+        if (!me) {
+            throw new Error('Failed to get user ID');
+        }
+
+        const member = room.getMember(me);
+        if (!member || member.membership !== "join") {
+            throw new Error(`User ${me} is not in room ${roomId}`);
+        }
+
+        return room.currentState.maySendStateEvent('set_widget', me);
+    }
+}